Mesh networks using commodity WiFi routers and OpenWRT. Presentation at Open Source Workshop #5 (7 Apr 2012) @CityU Hong Kong

1. Mesh networks
using commodity WiFi routers
and OpenWRT
Alexander List <alex@wurzel.at>
Open Source Workshop #5 (7 Apr 2012)
City University of Hong Kong

2. Network topologies
http://en.wikipedia.org/wiki/Network_topology

3. Mesh network
http://en.wikipedia.org/wiki/Wireless_mesh_network

4. WiFi
IEEE 802.11
2.4 GHz ISM band (100 mW EIRP), ch. 1-14
60 MHz → 3 non-overlapping channels (1/6/11)
5 GHz ISM band (up to 1W EIRP)
Indoor channels (5.15 – 5.25 GHz, ch. 36-48)
Outdoor channels (5.25 – 5.6 GHz, ch. 52-140)
Always check national regulation (HK: OFCA)

5. Typical WiFi deployment
(c) eTutorials.org

6. 802.11 modes
Infrastructure mode (STA → AP)
Home network
Office
Café
Ad-hoc mode (STA-STA)
Mac OS “create network” (AirPort menu)
Linux: iwconfig wlan0 mode Ad-Hoc
Ubuntu: using Network Manager

7. Commodity hardware
Linksys WRT54G series
GL runs Linux

8. WiFi chipsets

9. China: TP-Link
TL-WR703N: 57x57x18mm, ~RMB 95
57x57x18mm
Atheros AR7420, 4MB flash, 32MB RAM
1x 10/100 Mbit/s Ethernet, USB 2.0, 802.11n
TL-WR743ND: ~200 HKD
Atheros AR7420, 4MB flash, 32MB RAM
5x 10/100 Mbit/s Ethernet, 802.11n
TL-WR1043ND: ~390 HKD
Atheros AR9132, 8MB flash, 5x GigE, 3xMIMO

10. Buying hardware
Check http://wiki.openwrt.org/toh for support
Go for more flash (≥ 8 MB)
Detachable antennas
12V DC power supply
Several LAN ports

11. OpenWRT

12. OpenWRT
Linux kernel
Own build/packaging system
Originally derived from Linksys WRT54G
GPL sources
Active community, supports 100s of devices
Mesh network protocols available
Asterisk, MySQL, ...

13. Wireless mesh protocols
http://battlemesh.org/
OLSR, B.A.T.M.A.N., Babel, BMX, 802.11s, ...

14. Wireless community networks
Germany: Freifunk in several cities
Austria: FunkFeuer (120/200 nodes)
Athens: AWMN (2433 nodes)
Barcelona: guifi.net
Overview:
http://en.wikipedia.org/wiki/List_of_wireless_community_networks_by_region

15. FunkFeuer Graz

16. AWMN

17. Spain: guifi.net

18. Asia?!
India: AirJaldi
Indonesia: BWIC
Nepal: nepalwireless.net

19. What do we need?

20. Let's get this party started...
When:
Saturday, May 12, 2012, 14:00-17:00
Where:
DimSumLabs, 14/F, 100-102 Jervois Street,
Sheung Wan
Bring:
Laptop, WiFi router supporting OpenWRT

21. Thank you!